Projection of laser generated image

ABSTRACT

A multi-beam tool is disclosed which can perform square, plumb, and level function which may be required in a construction environment. The tool can generate in a preferred embodiment up to five orthogonal beams with two beams being plumb and three beams being leveled. Combinations of two level beams, or a level and a plumb beam in orthogonal arrangement can produce a square alignment set of beams. The tool includes in a preferred arrangement a self-leveling pendulum to which a laser and quad-mirror arrangement is secured. The self-leveling pendulum is dampened in order to allow the tool to settle down and provide alignment after the tool is positioned as desired.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is continuation of U.S. patent application Ser.No. 10/353,599 filed Jan. 28, 2003, which is a divisional of U.S. Pat.No. 6,542,304, filed May 16, 2000, which claims the benefit of U.S.Provisional Application No. 60/134,403 filed May 17, 1999 entitledSelf-Leveling Penta Laser Beam Device, and of U.S. ProvisionalApplication No. 60/159,524, filed Oct. 15, 1999, entitled Self-LevelingPenta Laser Beam Device. All of these applications are incorporatedherein by reference.

[0002] Additional References

[0003] Reference is made to U.S. Pat. No. 5,680,208, issued Oct. 21,1997, entitled GRAVITY ORIENTED LASER SCANNER, which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

[0004] In many instances it is desired to establish reference lines.This is particularly useful for construction, grading, and “do ityourself” activities. Traditional tools for these tasks include straightedges, rulers, protractors, squares, levels, and plumb bobs. More moderntools include laser alignment devices.

[0005] Laser alignment devices include simple pointers, pointers with abubble vial, self-leveling pointers, multiple beam pointers, and devicesthat produce a sheet of light. It is highly desirable to have multiplebeams that are mutually orthogonal. This is typically achieved byseveral partially silvered mirrors at 45 degrees to the laser beam. Thismethod requires placing the mirrors in precise alignment and securingthem with glue. Further, the mirrors should be extremely stable overtime and temperature. More beams require more mirrors at added expenseand complexity.

SUMMARY OF THE INVENTION

[0006] The present invention relates to improvements to this fieldrendering simpler, more stable and cost effective laser devices whichcan generate one or more laser beams for measuring, aligning, levelingand other purposes.

BRIEF DESCRIPTION OF THE FIGURES

[0007]FIG. 1 is a perspective view of an embodiment of a penta beamsplitter of the invention.

[0008]FIG. 2 is a perspective view of another embodiment of a beamsplitter of the invention.

[0009]FIG. 3 is a further embodiment of the invention which can be usedto project a pattern such as a pattern of cross hairs.

[0010]FIGS. 4a and 4 b are perspective and side sectional views of yetanother embodiment of the invention that allows for steering beams whichare at angles with respect to the main laser source.

[0011]FIG. 5 is a side sectional view of yet another embodiment of theinvention wherein the main laser beam can be focused by symmetricalcrimping of the housing of the embodiment.

[0012]FIGS. 6a and 6 b depict side sectional views of another embodimentof the invention, showing how the laser assembly is suspended by abearing mount.

[0013]FIG. 7 is a perspective view of another embodiment of theinvention using elliptical reflective mirrors.

[0014]FIG. 8 depicts an interference target resulting from the use ofdevice of FIG. 7.

[0015]FIG. 9 is a perspective view of another embodiment of theinvention using square reflective mirrors.

[0016]FIGS. 10a and 10 b depict interference targets resulting from useof the device of FIG. 9.

[0017]FIG. 11 is a perspective view of another embodiment of theinvention using rectangular mirrors.

[0018]FIGS. 12a, 12 b, 12 c depict interference targets resulting fromuse of the device of FIG. 11.

[0019]FIG. 13 is a side view of a pendulum laser mount with springcompensation.

[0020]FIG. 14 is a side view similar to FIG. 13 which allows for fieldcalibrations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] I. Penta Beam Splitter

[0022] The present invention (FIG. 1) achieves the much-desired featureof producing a series of mutually orthogonal beams with a singlesplitter. Further, the beams are mutually coincident, that is, the beamsall emanate from the same point.

[0023] The splitter in this embodiment is fabricated from a small blockor cylinder of aluminum 2. Other materials and fabrication techniquescan be otherwise employed. Four reflective mirror surfaces 8 a-8 d areproduced by a process known as “single point diamond turning.” Thisprocess is widely used to produce polygonal mirrors for laser printers.In one particular embodiment of the invention, four sections or portions10 a-10 d of the collimated beam 9 are reflected from the mirrorsurfaces. A fifth portion of the light 12 passes directly through a hole14 in the center of the block.

[0024] The angle of the mirrors must be precisely 45 degrees to theincident beam and have precise rotational symmetry. This is readilyachieved by optical tooling fixtures.

[0025] In this embodiment, light from laser diode 4 is directed througha lens and collimator 6. This collimated light is directed at mirrorblock 2.

[0026] In another embodiment, a similar effect could be achieved by useof a refractive device that employs total internal reflection orrefraction to produce a 90 degree bend. A small flat portion is createdon the tip of the device closest to the incoming beam to allow part ofthe beam to pass through undeflected, producing a fifth beam.

[0027] II. Beam and Disk Splitter

[0028] A related feature can be achieved by using a conical surface 16and hole 14 as depicted in the embodiment of FIG. 2. This produces aplane or disk of laser light 18, together with an orthogonal laser spot.

[0029] Various embodiments of the invention may include a multiplefaceted reflective device or devices having a mix of cylindrical andfaceted areas. For example, a device having twenty-four facets wouldyield 24 beams or spots, each separated from its nearest neighbor by anangle of 15 degrees. Larger areas could be used for four of the facets,which would make those four reflected beams brighter relative to theothers. This is useful in marking the major axes.

[0030] III. Cross Hair Projection

[0031] At short distances the beam may be too bright to use to easilycenter upon a reference line or point. In an embodiment of the inventionas depicted in FIG. 3, a masking element such as a holographic film 24,positioned on one or more of the laterally reflected beams 22 (or beams10 a, b, c, d of FIG. 1) can be used to project a more useful shortrange image such as a cross hair 28, or a series of concentric circles.An aperture 26 in the mask allows some light to pass through to be usedat a distance.

[0032] Alternatively, in other embodiments, a similar effect may beachieved by introducing intentional imperfections into the mirrorsurfaces.

[0033]FIG. 3 is simplified by using a half-silvered mirror as a beamsplitter. Alternatively, the beam splitting FIG. 1 could be used.

[0034] IV. Side Beam Steering

[0035] The four side beams produced by the embodiment of a penta beamsplitter of FIG. 1 are by design mutually perpendicular and coplanar,the accuracy of which being determined by the accuracy of the cuttingprocess. But they may be thereafter aligned or adjusted to be preciselyperpendicular to the central beam. A traditional approach would employ 4set screws to precisely deflect the mirror block.

[0036] A present embodiment of the invention (FIGS. 4a, 4 b) utilizes anovel approach to beam adjustment in mounting the laser assembly withina cylindrical enclosure 30 of deformable material, for example metal orplastic. The enclosure contains a series of beam exit holes 36 a-36 daround its circumference to allow the reflected beams exit the device. Aweb of deformable material remains between the holes. The method of beamsteering as embodied in the invention works by crimping the web 34formed between the side exit holes. Deforming an adjacent pair of websslightly shortens the cylindrical structure in that local region. Thiscauses the beam to rotate back about this location. Crimping andadjustments of the beam direction are noted by the angle θ in FIG. 4a.

[0037] This method of beam adjusting has the significant benefit ofeliminating the need for glue, which aids in manufacturing and long termstability.

[0038] V. Beam Focus by Symmetric Crimping

[0039] A technique similar to that of side beam steering described abovemay be employed to focus the laser diode, as shown in the embodiment ofFIG. 5. In this embodiment another series of holes 38 a-38 d (holes 38 cand 38 d are not shown as they are in the cut-away half of theenclosure) are introduced into the cylindrical enclosure, this timebetween the laser source 4 and the lens 6. A web 39 of material remainsbetween the holes. Bending all four webs the same amount causes theoverall length of the section to shorten. In practice, the diode may bepressed into the cylinder at a distance just longer than nominal focaldistance, and crimping applied to shorten the diode/lens separation byan amount 40 until the laser comes into focus. Typically, many metalshave some rebound after bending. This factor can be predicted andcompensated for by crimping past the focus point.

[0040] VI. Bearing Mount

[0041] A traditional means of producing a quality gimbal is with twopairs of roller bearings. The pairs must be precisely located and apreload must be applied to take out the clearance between the bearingsand races. An embodiment of the present invention (FIGS. 6a, 6 b)reduces this to a single pair of bearings 47, 48 suspended in achain-like configuration. The slight angle θ shown on the transversebeam 46 allows the weight of the pendulum 49, on which the laserenclosure 30 is mounted, to be distributed over both bearing units.

[0042] The pendulum arrangement shown in FIG. 6a and 6 b is hung fromthe double bearings 47, 48, and includes pendulum 49. Pendulum 49 mountsthe laser enclosure 40 which can include the laser enclosure depicted inFIGS. 1 and 2 by way of example. The enclosure of FIG. 1 with thequad-mirror is preferable. Still preferable, as is described more fullyhereinbelow would be the quad-mirror shown in FIGS. 9 or 11.

[0043]FIG. 6a is a cross-sectional view of the upper bearing 47 shown inFIG. 6b. The lower bearing 48 is mounted on a pin 46 which extends at anangle from the pendulum body 49. It is in this way that the lowerbearings 48 hangs down from the upper bearings 47, and the pendulum 49hands down from the lower bearings 48. At the base of the pendulum isthe damping weight 44. The damping weight 44 is generally comprised of aconductor and in particular, a copper conductor. In order for dampeningto occur, a magnet arrangement 45 is depicted. In a preferredembodiment, the magnet arrangement includes a soft iron horseshoe-shapedmount 46 which extends around the back side of the damping weight 44.Two magnets, such as magnet 51, are mounted at the ends of the horseshoe46. The horseshoe provides a return path for the magnetic flux in orderto assist and concentrating the magnetic field between the front facesof the magnets 51 in order to more efficiently damp the damping weight44. It is to be understood that in a preferred embodiment, a magneticarrangement of 45 would be placed on each side of the damping weight.The damping weight would swing through the arrangements and be damped byboth magnetic arrangements 45.

[0044] VII. Round Mirrors 54

[0045] The shape of the laser spot is of considerable interest. Thepractical need is to be able to identify and mark the center of thespot. In a squaring or plumb application this needs to be done in twoaxes. To facilitate this, a natural choice is round spots. The followingdescribes a novel method of producing them. It involves die casting thequad mirror, previously described, in aluminum. A feature of the deviceis four small posts 56 a-56 d surrounding a central hole 58 (FIG. 7).The end of each post is single point diamond turned to produce fourelliptical mirrors. The axial projection of each mirror is a circle.Thus, they act as apertures to project circular shafts of light in eachof 4 directions.

[0046] Round Spots Resulting From Round Mirrors

[0047] The smaller the circular apertures 56 a-56 d, the larger thelaser spots appear at a distance. This is due to the normal dispersionof light off of a sharp aperture. Since the laser light ismonochromatic, the wave front from one side of the aperture interfereswith the wave front from the other side. This results in a series ofcircular interference rings 59 (FIG. 8). The exact size and diameter ofthe central spot 60 from hole 58 and these rings 59 depends on thewavelength, distance to the target, and the aperture diameter. Aperturesin the range of 2 mm produce acceptable spots.

[0048] VIII. Square Mirrors 60

[0049] A novel alternative to the pyramidal mirror geometry proposed inthe above is to form four small mirrors into a quad-mirror arrangement60 with parallel sides (FIG. 9). This is readily accomplished by formingthe blank on a screw machine with a special profile for the end cone. Asquare aperture 64 is readily broached through the center. Four passesof a diamond-point fly-cutter then cuts four mirrors 62 a-62 b leavingthe conical section in-between. In use, this presents five similarapertures to the incident laser beam.

[0050] As can be seen in FIG. 9, the four mirrors meet each other atcommon corners which define the central square aperture 64. Corner 63 a,b, c, and c, at the sides of the four mirrors 62 a-62 d, do not gothrough the apex of the structure. In effect, the structure is truncatedin order to form the square aperture 64. The truncated structure formsthe square aperture 64 from which the four mirrors 62 a-62 d emanate.Due to this structure, this arrangement provides appropriateinterference pattern so that targets can be formed as described below.

[0051] Square Spots

[0052] The square central aperture produces a nominally square spot(FIGS. 10a, 10 b). As with the circular aperture, wave fronts fromopposite sides interfere, but in this case a series of spots are formedradiating in four directions (FIG. 10a). This creates a “cross hair”formation that is ideal for marking. The apertures formed by the mirrorsperform in a similar way. In the direction where parallel edges arepresented, interference spots are formed. In the other direction, therein only one sharp edge (FIG. 10b). The dispersion from this edgeproduces a “smear” along this axis. It is similar in brightness and sizeto the string of spots in the other direction. Thus a cross-hairappearance is produced.

[0053] IX. Rectangular Mirrors 68

[0054] The light from a laser diode is presented from a typicalcollimating lens as a short line segment, in which the light is spreadout more along one cross-sectional axis than the other. In oneembodiment, to better slice up this beam, the mirrors 70 a-70 b and 71a-71 b need be all the same (FIG. 11). Of further design considerationis the power distribution desired. For example, the up and down beamsmay not be desired to be as strong as the side beams, so the up and downreflectors may be designed to be smaller than the lateral or sidewaysreflectors. A wide range of power distributions is possible with minimalloss in the inter-mirror space.

[0055] With respect to FIG. 11, the configuration of the quad-mirror 68includes the following. The rectangular aperture 74 has four corners 75a-75 d. It is from these four corners that the mirrors 70 a, b, and 71a, b, extend. Thus, as previously indicated, the corners of the mirrorsdo not all originate from the same apex. Viewing mirror 71 a, it isevident that it is defined by substantially parallel side 72 a, b, whichoriginate respectfully from corner 75 a, 75 b. Similarly, thesubstantially parallel sides 73 a, 73 b of the mirror 70 b originatefrom corners 75 b, 75 c, respectively. This same pattern occurs for theother mirrors 70 a and 71 b. In such an arrangement, the cross-hairpatterns are created on the desired target. Also, as the sizes of themirrors can be made to have different areas, the intensity of the beamcan be made to vary.

[0056] Rectangular Spots

[0057] The spots (FIGS. 12a, 12 b, 12 c) produced by rectangular mirrorsare approximately rectangular. The direction of interference spots andsmears are similar to those described above with respect to squaremirrors. The spacing of the spots depends on the width of the aperturein each direction, so the spacing of the spots may not be the same foreach direction.

[0058] X. Spring Compensation

[0059] The embodiment of FIG. 13 includes a pendulum 80 which hangs downfrom a gimble mount 76. The gimble mount allows the pendulum to swing intwo directions of freedom. Hanging down from the gimble mounts is thecoil wire 78 which is used to power the laser assembly 35. The laserassembly includes the driver board 41 to which the wire is attached.Hanging down from the pendulum is the damper 44. The damper 44 is dampedby the damping arrangement 45 as previously described.

[0060] The laser Diode Optical assembly in enclosure 40 requires twoelectrical connections. This is typically achieved by the use of veryfine copper wires. But such wires present a surprisingly significantspring torque on the pendulum. The nozero stiffness has the property ofdipping the beam if the housing is rotated forward. This is one of thedominant limitating factors in miniaturizing a pendulum assembly. Makingthe pendulum longer, the service loop longer, and/or coiling the wiresare techniques widely used in existing system.

[0061] An embodiment of the invention has the wires formed into a coil78 and used as an extension spring. Stretched across the axis ofrotation of the pendulum 80 it functions as an “over center mechanism”.This has the inverse property that the beam pos up if the housing istilted forward.

[0062] By carefully matching the bending stiffness against the overcenter spring the two effects are largely canceled. Although FIG. 13shows a sectional view through one dimension, this effect workssimultaneously in all degrees of freedom of the pendulum.

[0063] A further benefit of this method is that the over center springacts to relieve gravitational drag torque on the bearings. This may makeit possible to use still shorter pendulums and rollerless bearings.

[0064] XI. Field Calibration by Spring Compensation

[0065] A feature of the invention is field calibration. This istypically accomplished by adjusting screws 78 a, b, mounted in thependulum. In the field, should the laser beams come out of alignment,the alignment can be corrected by adjusting the distribution of weighton the pendulum. This is accomplished by adjusting the position of theadjusting screws 78 a, b, causing the screws to move into or out of thependulum.

[0066] Initial alignment during manufacturing can be accomplished byremoving weight from the damper 44 by for example a drilling techniquein order to align the laser beams with preestablished targets.

[0067] With respect to another type of field alignment, the axialpositioning of the over center spring is important. If off-axis it wouldleave a net torque on the pendulum. A novel feature of invention allowsfor such a misalignment to be used to field calibrate the pendulum. Asshown in FIG. 14, screw pairs 82, 84 can manipulate the spring mountingpoints 86, therein adjusting the orientation of the suspended laserassembly. This has the desirable property that the user need not comeinto contact with the delicate pendulum assembly.

Industrial Applicability

[0068] The present invention provides for multiple embodiments which cangenerate multiple laser beams for measuring, aligning, leveling andother purposes. In addition, the embodiment are for beam steering andfocusing as well as mounting of the laser itself.

What is claimed is:
 1. A method for using a laser alignment device toproject a laser generated image at a distance, the method comprising:providing a laser source to produce a beam of laser radiation; andpositioning a transmission mask in the path of the beam to modify theshape of the transmitted beam.
 2. The method of claim 1 wherein thetransmission mask has a substantially opaque region, and a substantiallytranslucent region in the shape of an image.
 3. The method of claim 2wherein the mask contains an aperture within the substantiallytranslucent region.
 4. The method of claim 1 wherein the transmissionmask is formed from a holographic film.
 5. The method of claim 4 whereinthe transmission mask contains a holographic image within theholographic film.
 6. The method of claim 5 wherein the transmission maskcontains an aperture in the holographic film within the holographicimage.
 7. The method of claim 1 further comprising positioning areflective element in the path of the beam of laser radiation to produceone or more laterally reflected beams.
 8. The method of claim 7 whereinthe transmission mask is positioned in the path of a laterally reflectedbeam.
 9. An apparatus for use with a laser alignment device forprojecting a laser generated image at a distance, comprising: a lasersource to produce a beam of laser radiation; and a transmission mask,positioned in the path of the beam, to modify the shape of thetransmitted beam.
 10. The apparatus of claim 9 wherein the transmissionmask has a substantially opaque region and a substantially translucentregion, the translucent region on the shape of an image.
 11. Theapparatus of claim 10 wherein the mask contains an aperture within thesubstantially translucent region.
 12. The apparatus of claim 9 whereinthe transmission mask is formed from a holographic film.
 13. Theapparatus of claim 9 wherein the transmission mask contains aholographic image within the holographic film.
 14. The apparatus ofclaim 13 wherein the transmission mask contains an aperture in theholographic film within the holographic image.
 15. The apparatus ofclaim 9 further comprising a unitary reflective element positioned inthe path of the beam to produce a plurality of beams, the reflectiveelement defining a central aperture, at least two substantially planarreflective surfaces positioned around the central aperture for creatinglaterally reflected beams from the beam of laser radiation, and othersections located in-between the substantially planar reflective surfacessuch that the substantially planar reflective surfaces are not adjacentone another.
 16. The apparatus of claim 15 wherein the transmission maskis positioned in the path of a laterally reflected beam.
 17. Theapparatus of claim 15 wherein the planar surfaces have elliptical crosssections.
 18. The apparatus of claim 15 wherein at least one of thereflective surfaces has a largest cross section than a second of thereflective surfaces.
 19. The apparatus of claim 9 further comprising areflective element positioned in the path of the beam to produce atleast one laterally reflected beam.
 20. The apparatus of claim 9 furthercomprising a quad-mirror having reflective surfaces and an apertureextending through the center of the quad-mirror.
 21. The apparatus ofclaim 9 further comprising a collimating lens and an enclosure ofdeformable material, wherein the lens and laser source are at leastpartially positioned within the enclosure and the lens is positioned inthe path of the beam of laser radiation.
 22. The apparatus of claim 21wherein the enclosure may be symmetrically deformed to modify thedistance between the lens and the laser source.
 23. The apparatus ofclaim 21 further comprising a reflective element positioned within theenclosure of deformable material in the path of the collimated beam toproduce at least one laterally reflected beam.
 24. The apparatus ofclaim 23 wherein the enclosure of deformable material further comprisesholes in the enclosure to allow passage of laterally reflected beams.25. The apparatus of claim 23 wherein the enclosure of deformablematerial may be asymmetrically deformed to rotationally deflect thereflective element relative to the collimated beam.
 26. The apparatus ofclaim 9, further comprising a gimbal-mounted pendulum allowing forsubstantially pendular motion relative to an axis of rotation, whereinthe laser source is mounted on the pendulum.
 27. The apparatus of claim9, further comprising a conductive spring that provides power to theapparatus and a pendulum, wherein the apparatus is hung from thependulum.